(a) Field of the Invention
The present invention relates to an optical microscope, and more particularly it pertains to a surgical microscope.
(b) Description of the Prior Art
In surgical operations conducted by utilizing a surgical microscope, there is the necessity for the surgical operator's assistant who, standing by the side of the operator, assists the latter, to constantly observe the same region of the patient's body as that observed by the operator. As the known means for materializing this kind of demand, there may be enumerated, for example, a device of the type (I) as shown in Japanese Patent Publication No. Sho 55-10174 and a device of the type (II) as shown in Japanese Utility Model Publication No. Sho 55-39364.
The device of the type (I) mentioned above is schematically shown in FIGS. 1 and 2. A specimen not shown for observation is located at a position on the downward extension of a pair of operator's bilateral observational optical axes "a". In connection with this, there is disposed on said optical axes "a" a set of members comprising a common objective lens 1, bilaterally arranged auxiliary lenses L.sub.a and L.sub.b, and also light beam splitting prisms P.sub.1 and P.sub.1 '. In the straightforward direction of transmission through these light beam splitting prisms P.sub.1 and P.sub.1 ', there extend the operator's observational optical axes "a", and on their extensions, there is further disposed an observational optical system not shown. The operator surgeon (hereafter will be referred to merely as "operator") makes an observation by utilizing this observational optical system. On the other hand, in the directions in which the light beams are split and deflected by the light beam splitting prisms P.sub.1 and P.sub.1 ', there extend a pair of assistant's observational optical axes "b" as shown by chain lines. On said optical axes "b" of the assistant, there is provided an assistant's observational optical system which comprises prisms P.sub.3, P.sub.3 ', P.sub.4, P.sub.4 ' and ocular lenses 5, 5'. Accordingly, by utilizing the operator's observational light beams which have been so split by the light beam splitting prisms P.sub.1 and P.sub.1 ', the assistant is enabled to observe the same observational images I.sub.n and I.sub.n ' as for the operator.
Also, the above-mentioned type (II) is of the arrangement as shown in FIGS. 3A to 3C that one pair of operator's observational optical axes "a" and one pair of assistant's observational optical axes "b" are accommodated independently of each other pair within a barrel, or as shown in FIGS. 4A to 4C, three optical axes using, in common, one of the bilateral view field optical paths are provided within a barrel, so that when the observation is conducted simultaneously by the operator and his assistant in directions crossing each other at right angles, both the operator and his assistant are able to obtain a stereoscopic image of the same region of the human body. It should be noted here that in these drawings, reference numerals 2, 2' represent zoom lenses; 3, 3' image focusing lenses; 4, 4' reflection mirrors, and 5, 5' ocular lenses.
However, with the above-mentioned type (I), there is the inconvenience that, while the operator is able to have his own normal stereoscopic view, the bilateral view field images afforded by the assistant's observational optical system are the bilateral view field images exactly as viewed at the operator's own position. These latter images for the assistant, therefore, differ from those bilateral view field images which would be viewed at that actual position of the assistant which is different by, for example, 90.degree. from that of the operator, so that the assistant is unable to have a stereoscopic view in the normal way. For this reason, the assistant is placed in a difficulty in providing subtle and delicate assistance to the operator concerning the site requiring a surgical operation. Thus, there have been the problems that the risk of surgical operation is augmented and that the operation requires an extended period of time.
Also, in case of the above-mentioned type (II), while there arise no such problems as those occurring in the above-mentioned type (I), the number of optical axes which are to be accommodated in the barrel increases faster than in the case of an ordinary surgical microscope, so that the barrel per se tends to become large in size, impairing the operability of the device on the part of the operator and his assistant, and along therewith there arises the necessity for centering the four optical axes and also for adjusting the confocus of these optical axes, leading to the problem that the device becomes expensive as compared to the ordinary microscope comprising two optical axes.